More than half of the women born during Japan's second postwar baby boom from 1971 to 1974 had not had any children by age 30, according to statistics released Friday by the Health, Labor and Welfare Ministry.

Coupled with an earlier prediction that the number of women of childbearing age -- 15 to 49 -- will continue to decline over the coming decade or more, the ministry is concerned that the fall in the birthrate will accelerate.

"(Because) numerous women in the second baby boom generation have few children, (this) could mean the birthrate will fall at a faster rate, and the population will further decline," a ministry official said.